Stocks ended higher Tuesday, helped along by better-than-expected factory data and strong auto sales. The Dow fared the best, rising 0.6%. The S&P 500 and the Nasdaq gained 0.5% each. The S&P is only 6 points from its October 2007 intraday high of 1576. Preliminary data showed NYSE and Nasdaq volume coming in about 10% higher than Monday's levels. It was a mild accumulation day at best for the indexes because volume was below average again on the